The present invention relates to heat exchangers and heat transfer fins used in heat exchangers such as air-cooled heat exchangers and, more particularly, to heat transfer fins which provide small resistances to the passage of air and exhibit excellent heat transferring performance and to heat exchangers incorporating such heat transfer fins.
In general, a heat exchanger, such as an air-cooled cross-fin-tube type heat exchanger used in an air conditioner, refrigerating machine or the like, comprises a large number of fins formed of aluminum sheets disposed in parallel and a plurality of heat transfer tubes extending through the parallel fins, with the heat transfer tubes and the fins being closely attached to each other by a suitable method such as tube expanding operation, and with the ends of the heat transfer tubes being connected together by U-shaped bends. One heat exchanging fluid, such as cold water, hot water or a refrigerant, is allowed to flow through the heat transfer tubes, while another heat exchanging fluid, which may typically be air, is allowed to flow outside the tubes at a suitable speed, so that exchange of heat is effected through the tube walls and the fins.
One type of heat transfer fins which may be used in such a heat exchanger is disclosed in, for example, Japanese Patent Laid-Open Publication No. 62-52896 and corresponding U.S. Pat. No. 4,791,984. A fin of this type provides a large resistance to the passage of fluid in the vicinity of the central portion of the fin that is disposed between two adjacent heat transfer tubes, while the fin provides a small resistance to the passage of fluid at the end portions of the fin that are on the opposite sides of the central portion, thereby enhancing the heat transferring performance.
Recent years have seen the demand for further enhancement in the heat transferring performance. However, since the above-described conventional fin comprises a single small piece of metal, there is a limit to any further reduction in the size of the fin from the viewpoint of rigidity, making it impossible to achieve any further enhancement of the heat transferring performance.